When Google bought the advertising network DoubleClick in 2007, Google founder Sergey Brin said that privacy would be the company’s “number one priority when we contemplate new kinds of advertising products.”

Last summer, Google reworded its privacy policy to say that browsing habits “may be” combined with what the company learns from the use Gmail and other tools.

The change is enabled by default for new Google accounts. Existing users were prompted to opt-in to the change this summer.